396 0. C. Marsh—New Jurassic Mammals. 
center, the slit being nearly to the closed end. This slit divides 
the tube equally and gives two vibrating prongs, analogous to 
those of a fork. To bring the prongs into unison with the 
column of air between them, the tube is put in a lathe and 
turned thinner until the desired point is reached and the two 
are in unison. Thereupon the sound of the fork is powerfully 
reinforced. 
Art. XLIX.—Notice of New Jurassic Mammals ; by Prof. 
O. C. MaRsH. 
ADDITIONAL remains of mammals from the Jurassic of the 
ky Mountains indicate that this class constituted an impor- 
tant element in the Mesozoic fauna of this country. The forms 
already described,* as well as those noticed below, show more- 
over, such a resemblance to known types from the Purbeck of 
England, that some connection between the two faune is clearly 
implied, and future discoveries will be awaited with interest. 
lent preservation. This specimen differs widely from the 
Right lower jaw of Ctenacodon serratus, Marsh ; about four times natural size. 
a. incisor; 6. condyle; c. coronoid process. 
_ This lower jaw is short and massive. Its outer surface 15 
marked by a strong ridge, which begins below the first pre 
Molar, and is continued to the base of the coronoid process. 
____- * This Journal, vol. xv, p. 459, 1878; vol. xviii, pp. 60 and 215, 1879. 
Journal Geological of London, vol. xiii, p. 261. 1857. 
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